Carbon dioxide absorber



Aug. 19, 1958, w. w. HAY 2,848,309

CARBON DIOXIDE ABSORBER Filed Oct. 23. 1956 2 Sheets-Sheet 1 ATTORNEY 8.AGE NT Aug. 19, 1958 w, w. HAY 2,848,309

CARBON DIOXIDE ABSORBER Filed Oct. 25, 1956 v 2 Shee'ts-Sheet 2 FIG. 3

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ATTORNEY AG ENI United States Patent CARBON DIOXIDE ABSGRBER Wayne W.Hay, Madison, Wis, assignor to Air Reduction Company, Incorporated, NewYork, N. Y., a corporation of New York Application October 23, 1956,Serial No. 617,875

12 Claims. (Cl. 23-484) This invention relates to absorbers employed inanesthetic administering apparatus for the removal of carbon dioxideand, more particularly, concerns improvements therein. In such absorberdevices a canister, or container, generally is provided for holding asupply of a carbon dioxide absorbing agent, such as soda lime, withwhich the gases in the anesthetic circuit are contacted. The carbondioxide in the patients exhalation is selectively removed, for example,by soda lime, through chemical action; the carbon dioxide reacting withthe soda lime and the remaining gases being recovered and recycled tothe patient. The process may be carried out continuously until thecharge becomes exhausted whereupon it is replenished with a freshabsorbent.

It is extremely important when administering anesthetic agents topatients by conventional administering apparatus that the carbon dioxideabsorber function properly at all times. Otherwise, the carbon dioxidecontent of the gases in the breathing circuit may rapidly increase abovea safe level, such that adequate ventilation and oxygenation of thepatient cannot be maintained. Accordingly, extreme diligence isexercised by the anesthetist or other personnel responsible for theproper functioning of the administering apparatus in examining theequipment before and during administration. In conventional types ofabsorbers that have been employed heretofore, various unsatisfactoryfeatures have been observed. It has been found that many presentlyavailable absorbers are cumbersome and of such intricate constructionthat the inspection or replacement of the absorbent charge, frequently,is quite involved. The time consuming operations for such servicing arenot only a hindrance to the normal care and maintenance of the apparatusbut are seriously objectionable where it may become necessary to inspector replace the charge during anesthesia.

The inconvenience involved in the use of present absorbers is furtheremphasized by the fact that many of these devices, necessarily, have arelatively small capacity for the charge of absorbent. Thus, theprocedure of replenishing the charge where its absorbing power isexhausted must be repeated at more frequent intervals. In addition, manyof the absorbers currently in use are of such design that the depletionof the absorbent occurs non-uniformly leaving a portion of the chargesubstantially unchanged while other portions have been substantiallyexhausted. Although a considerable portion of the charge may still befresh, its replacement is necessary to insure proper functioning of theabsorber and a safe margin of absorptive capacity. Consequently,considerable waste and ineflicient use of the absorbent material isincurred. A further source of objection has been encountered in thedifliculty of cleaning the absorber devices of conventionalconstruction, and particularly of removing the caked deposits ofexhausted charge material which accumulate therein during use. In manyabsorbers, the points at which these deposits accumulate are notaccessible and considerable difiiculty and inconven- Cir 2 ience isencountered in properly cleaning the apparatus.-

It is, therefore, an object of the present invention to provide a carbondioxide absorber for anesthetic admmistering apparatus which is ofcompact construction and which has a removable canister for holding asupply of carbon dioxide absorbent material, wherein the removal andreplacement of the canister for replenishing the absorbent and servicingthe absorber is greatly simplified.

It is a further object of the invention to provide such an absorberhaving a housing on which the canister is removably supported, in whicha more uniform distribution of the gas mixture through the absorbentmate rial and a more efficient utilization of the absorbent is afiorded.I 7

It is a further object of this invention to provide a carbon dioxideabsorber having a housing including inlet and outlet connections adaptedto be placed in a closed anesthetic administering circuit, which isarranged to receive at a bottom portion thereof an open-top canisterregistering with openings in said housing for circulating the anestheticgases therethrough.

It is a further object of the invention to provide a carbon dioxideabsorber having a detachable canister including a removable down-tubeunit carried therein, having a screen on which the bed of absorbentmaterial is supported and which is completely accessible for cleanmg. g

It is a further object of this invention to provide such an absorberhaving a housing with a delivery and a discharge port in the bottomthereof and an open-top canister seated thereon encompassing said ports,wherein said canister contains a removable down-tube unit having ascreen at its lower end for supporting an absorbent bed, and registeringat its upper end with one of said ports whereby respiration'gases may becirculated through said canister and said absorbent bed.

It is a further object of the invention to provide such an absorberhaving a detachable, open-top canister, and

an integral down-tube and screen assembly that is removable from thecanister, in which the upper end of the down-tube is arranged to beinserted in one of the port openings in the absorber housing and whereinsaid tube is automatically aligned with said opening when the canisteris placed in seated position.

A still further object of the present invention is to provide anopen-top canister for an absorber having fastening means for securingthe canister in seated position against the bottom of an absorberhousing, including an adjusting member disposed at the bottom side ofsaid canister and means projecting upwardly through the canister fordetachably engaging the absorber housing.

A still further object of the invention is to provide an absorber havingsuch a detachable canister unit wherein the fastening means is carriedby the canister, and the bottom of the canister is provided with arecess for accommodating the adjusting portion of the fastening means,so as to permit the canister to stand on its base in an upright positionwhen detached from the absorber.

A still further object of the invention is to provide in such a canisterfor carbon dioxide absorbers, a resilient biasing means interposedbetween the canister and said fastening means effective to urge saidfastening means in an upward direction and means for automaticallydisposing said fastening means in position for engagement in theabsorber housing, when the canister is seated.

A still further object of the invention is to provide such a detachable,open-top canister for a carbon dioxide absorber housing, wherein theremovable down-tube and screen assembly are axially disposed in thecanister; and said fastening means extends co-axially upwardly inside ofsaid down-tube and is threadedly engaged in the absorber housing.

thereof.

A still further object of the invention is to provide such a detachablecanister for absorber apparatus having a concave bottom in which theabsorbent-bed-supporting screen member rests on the bottom of thecanister and is. shaped relative thereto to form a chamber between thescreen and the bottom ofthe canister of a gradually diminishingcross-sectional area in an outward radial direction, and in which thedepth of the bed increases progressively, toward the outer stratathereof, thereby to distribute the flow of gas uniformly through theabsorbent charge.

Other objects and advantages of the present invention may be more fullyunderstood by referring to the following description of a preferredembodiment thereof in which reference is made to the accompanyingdrawings in which;

Fig. 1 is a perspective yiew illustrating a carbon dioxide absorberincluding an absorber housing and an open-top detachable canistermounted on the bottom thereof, embodying the features of the presentinvention;

Fig. 2 is a top plan view of the absorber housing seen in Fig. 1;

Fig. 3 is a full vertical section showing the absorber housing andcanister taken along the line 33 in Fig. 2, looking in the direction ofthearrows;

Fig. 4 is a sectional plan view of the absorber housing taken along theline 4-4 in Fig. 3, looking in the direction of the arrows;

Fig. 5 is a sectional plan view taken through the canister along theline 55 in Fig. 3, looking in the direction of the arrows;

Fig. 6 is a partial vertical section taken through the axis of thecanister by-pass valve, mounted on the absorber for adjusting the flowof gases through the canister, taken along the line 6-6 in Fig. 2; and,

Fig. 7 is a schematic drawing illustrating the gas circuit formed by theabsorber and canister.

A carbon dioxide absorber is designated generally at 10 in Figure 1 ofthe drawings, having a housing 12 and a canister 14 detachably mountedat the underside The canister holds a supply of a carbon dioxideabsorbent, such as soda lime. Inlet fitting 16 and outlet fitting 13 areadapted to be connected by means of conduits 20 and 21 to the usualanesthetic administering apparatus, as will be more fully describedhereinafter, to form a closed anesthetic administering circuit asillustrated for example by the J. .A. Heidbrink, United States PatentNo. 2,121,196. In such a circuit, an anesthetic gas mixture, uponexhalation by a patient, is delivered to the absorber and circulatedthrough the canister 14, and thence recycled to the patient. A canisterby-pass valve 22 is provided in the absorber to control the proportionof gas that is circulated through the canister so that, in this way, theconcentration of carbon dioxide in the respiration gases may bemaintained at any desired level. This manner of operating absorberdevices for closed anesthetic circuits is well known and is efiectiveparticularly when it is desired to stimulate the patients voluntaryrespiration, by maintaining, temporarily, higher than normal carbondioxide concentrations. The absorber is equipped with a fixture 23 forsupporting the absorber, which may be attached, for example, to aconventional anesthetic machine, not shown.

The inlet fitting 16 carries the customary exhalation check-valve 24 aswell as a rebreathing bag 26 and an adjustable pressure relief valve 28.An inhalation checkvalve 30 is mounted in the absorber housing and apressure gage 32 also is fixed thereon to indicate the pressure in theabsorber circuit. The check-valves 24 and 30 are of well knownconstruction and are of the type, as illustrated schematically in Figure7 having a gravity-loaded valve disc 33, and an annular knife-edge seat34. Each of the valves has a transparent cap 35 through which thefluctuations of the valve disc produced by the patients breathing may beseen. The relief valve 28 is also of conventional design and isillustrated schematically in Figure 7 by the spring loaded valve disc36, which vents the absorber circuit to the atmosphere when the pressureexceeds the valve setting. A vaporizer 38 of any suitable design isattached to the absorber outlet 18. The vaporizer contains a supply of avoiatile liquid anesthetic agent, such as ether, which is vaporized andadministered to the anesthetic circuit in controlled amounts byadjustment of the control knob 35. The construction and operation ofsuch vaporizing means is well known to those skilled in the art andforms no part of the present invention.

Figure 7 shows the absorber 10 schematically and illustrates its flowcircuit and the manner in which a patients gases are circulated throughthe absorber housing and canister. The control of the gases passedthrough the canister is illustrated in the circuit by the alternatepositions of the canister by-pass valve 22 shown in solid and dottedlines, which will be more clearly understood thereinafter. Also shown inthe absorber circuit is an inlet 40 such as is conventionally providedin a closed anesthetic circuit, through which fresh gas such as oxygenis added to replenish the oxygen consumed by the patient, or throughwhich gaseous anesthetics such as cyclopropane or nitrous oxide may besupplied. It will be understood to those skilled in the art that theapparatus comprising the closed breathing circuit may be arranged invarious ways and, as will become evident in the following description,the present invention is not limited to the specific breathing circuitin which the absorber is employed.

Referring now to Figure 3, it will be seen that the absorber canister 14comprises an enlarged cylindrical container having an inverted,cone-shaped bottom 42 and an open-top 44 seated within a cylindricalrecess 46 on the bottom of the absorber housing. The recess 46 forms ashoulder 47 having a gasket 48. against which the upper edge of thecanister is pressed to form a gastight seal. A retaining screw forsecuring the canister has an enlarged knob '50 bearing upwardly againstthe bottom of the canister and an elongated shaft 52, the upper end 54of which is threadedly received in a bushing 56 carried in the absorberhousing. The knob is threaded on the shaft 52 and locked thereon bymeans of a set screw 58. The retaining screw is mounted in the canisterby means of a spring 60 carried on a reduced portion 62 of the shaft.The spring is compressed between a washer 64 forced against the shoulderformed by the reduced portion of the shaft and a washer 66 which seatson the bottom 42 of the canister against the opening 67 through whichthe screw shaft projects. The pressure of the spring 60 thus urges thecanister retaining screw up Wardly, maintaining the head 50 in resilientengagement with the bottom of the canister. The spherical head portion68 of the retaining screw provides a bearing surface against the bottomof the canister and facilitates adjustment of the retaining screw toengage the threads 54.

It will be noted that the bushing 56 has a chamfered opening which isadapted to facilitate the insertion of the threaded end of the retainingscrew. In placing the canister in position on the absorber housing, thisconstruction is highly advantageous since it will be seen that as thecanister is raised towards the seating gasket 48 the upper end of theretaining screw comes into abutment with the bushing 56 before thecanister is seated. As further upward movement of the canister iscontinued, the spring 60 is compressed and produces an upward thrust onthe retaining screw. This thrust, assisted by the chamfered opening ofthe bushing is sufficient, automatically, to center the retaining screwagainst the bushing so that, when the canister is fully seated, theretaining screw may be tightened without the necessity of hunting tothread it into the bushing.

It Will be noted as a further significant feature of the aboveconstruction that the canister retaining screw is at all times carriedby the canister and that the external adjusting knob 50 is recessed inthe inverted bottom of the canister so as not to protrude beyond thebase formed by the bottom edge 70 thereof, as seeen in Figure 3.Consequently, when the canister is removed from the absorber, it may beplaced on any flat surface and will be entirely self-supporting. Inaddition, when the canister is picked up and returned to position forattachment to the absorber housing the retaining screw is alwaysimmediately accessible for tightening. Should it be necessary todismantle the canister and the retaining screw, the set screw 58 isreleased and the knob 50 threaded ofi of the lower threaded end 71 ofthe screw shaft 58. This permits the shaft of the retaining screw to bewithdrawn through the top of the canister. To reassemble, the washers 64and 66 and spring 60 are placed on the lower end of the shaft, as shown,which is again inserted through the canister and the knob 50 reattachedto the protruding, lower end.

Disposed within the canister 14 is a down-tube 72 which is rigidlyattached at its lower end to a perforated plate or screen 74 of asubstantially conical shape and which is provided with an in-turned rim75 on which the screen and down tube assembly are supported on thebottom 42 of the canister. The screen is relatively rigid and is adaptedto support thereon a bed of the carbon dioxide absorbent placed in thecanister. The apex angle of the cone-shaped screen, it will be seen, isslightly smaller than that of the conical bottom 42 of the canister soas to create therebetween a chamber 76 of gradually diminishingcross-section. At its upper end, the tube 72 is received in an opening78 which, it will be seen, has a chamfer 79 to facilitate the entranceof the upper portion of the tube 72 therein. The down-tube thuspositioned communicates with a delivery chamber 85} within the absorberwhich, as will later be described, communicates with the absorber inlet16.

The tube 72 carries at a point toward its upper end a plurality ofradially extending ribs 81 whose construction may best be seen byreference to Figure 5. As shown therein, the ribs are formed by a groupof three arcuate segments secured at their center points to the tube 72,such as by soldering or riveting, and joined together at their outerends. Thus, each of the outer ends extends an equal radial distance fromthe tube 72 and corresponds substantially to the spacing of the insideof the canister 14, so that the ribs formed by the segments act asguides to center the down-tube within the canister.

The lower screen member 74 also assists in centering the down tube bythe engagement of its rim 75 with the bottom 48 of the canister, whichengagement it will be seen urges the screen into axial alignment withinthe canister as the weight of the down-tube assembly and absorbentcharge supported thereon bear on the bottom of the canister. Theretaining screw 52 is also provided With a plurality of radial ribs 82,also seen in Figure 5, which co-act with the interior of the tube 7 tocenter the shaft 48 therein and assist in its proper engagement with thebushing 56 for securing the canister.

It will be seen that the above construction greatly facilitates theprocedure for mounting the canister on the absorber housing, which, infact may be done entirely by feel. This may be done, for example, bytilting the canister slightly and raising it toward the bottom of theabsorber so that its upper edge is placed against the inside of therecess 46. The canister is then straightened to its upright position,while maintaining its upper edge against the inside of the recess 46,which automatically brings the entire upper rim 44 of the canister intoseated position against the annular absorber gasket 48. At the sametime, the aligning means abovedescribed effects the alignment and theinsertion of the tube 72 into the port 78 and automatically brings theretaining screw into confronting position for engagement with thebushing 56. The chamfer 79 in the opening 78, it will be seen, should besufiicient to permit the entry of the tube 72 therein when the canisteris seated in accordance with the procedure above-described. The opening78 is slightly larger than the tube 72 to facilitate its insertion andavoid binding, but preferably is as closely fit as otherwise possible toreduce leakage around the tube.

Preferably, the guiding ribs 81 carried by the downtube are located at alevel corresponding to the level with which it is desired to fill thecanister. Thus, when the canister is charged with a carbon dioxideabsorbing material, such as soda lime, which preferably is in granularform, the material is added to form a bed extending from the supportingscreen '74 up to the level of the radial guide ribs. In this manner, aconvenient means is provided for indicating the desired amount of chargeso that a small space is insured at the top of the canister above thecharge bed. This space communicates with an outlet opening 83 throughwhich the gases, after passing through the absorbent bed, are dischargedto an outlet chamber 84 in the housing. Thechamber 84, as will later bedescribed, connects with the absorber outlet 18.

The internal construction of the absorber housing through which theanesthetic gases are circulated and conducted to and from the canistermay best be seen by reference to Figures 2, 4, 5 and 6. Referring toFigure 4, a partition 35 forms one wall or" the chamber 84 and separatesthis chamber from an inlet chamber 86 which receives the respirationgases from the inlet fitting 16. The chamber 86 is also enclosed by apartition 87 which divides this chamber from the delivery chamber 89.The outlet fitting 18 through which the gases are returned to theanesthetic delivery circuit connects with a chamber 88 in the absorberenclosed by partition members 89 and 9b. The opening for receiving thefresh gas inlet 40 is shown in the chamber 88. The canister by-passvalve 22, shown externally in Figure l, is pro-- vided with a Web 22 asseen in Figure 4 which when positioned as shown by the dotted linesforms a continuous Wall together with the aligned partitions 87 and 39.In this position of the control valve, all of the gas delivered to theabsorber through the inlet fitting 16 is passed from the deliverychamber 86 directly to the discharge chamber 88 and thence returned tothe circuit through the outlet fitting 18; none of the gases arecirculated through the canister. When the valve is rotated 90 such thatthe web 22' is in the position shown by the solid lines in Figure 4, anopening is created between the chambers 86 and 80. In this case, all ofthe gases delivered to the absorber pass into the chamber 3t and thencedownwardly through the tube 72 of the canister, to the bottom,distributing chamber 76 seen in Figure 3, and upwardly through theabsorbent bed supported in the canister on screen '74. The opening 83through which the treated gases are discharged from the canister anddelivered to the absorber chamber 34 is somewhat kidney-shaped, as canbe seen in Figure 4-. The web 91 extending across the chamber 84 doesnot form a partition, but is merely a structural rib member forstrengthening the absorber housing which, preferably, is a casting. Itwill be seen that a partition 92 forms an extension of partition 87 andseparates the chamber Stl from the chamber 84. Together with the web 22'of the control valve and partition 91'), the partition 92 forms acontinuous wall, when the valve 22 is in the full line position showndividing the inlet chamber 86 and chamber 84) from the dischargechambers 84 and 88. It will be readily apparent that, when the controlvalve 22 is rotated to a position intermediate the two positionsillustrated in Figure 4, the gases delivered to chamber 86 will bedivided, a portion thereof being circulated through the canister and aportion thereof passing directly to the discharge outlet of theabsorber. in this manner, it is pos sible to control the level of carbondioxide concentration in the breathing circuit, since the gases passingdirectly to the outlet will retain their carbon dioxide content.

The construction of the control valve 22 is more fully shown in thesectional view of Figure 6 wherein it will be seen that the web 22'thereof forms a part of a cylindrical valve stem 94 that is receivedwithin an opening 95 in the absorber housing. The valve stem hasopposite grooves 96 and 97 on either side of its web, or partition 22',which form openings through which the gases are conducted between thechambers interconnected by the setting ofthe valve. The valve stem isrotatably seated in the valve housing by means of a retaining screw 93threaded into the valve stem and resiliently biased by a spring 99 tomaintain the valve in frictional seating engagement. A shoulder 106 onthe upper side of the valve provides a bearing surface which rests on acorresponding seating surface 102 formed on the top of the valve body.Also seen in this figure and further illustrating the construction ofthe absorber housing is the vertical elevation of partition 87 dividingthe chamber 86 and the chamber 35 of the absorber. The partition ispartiatiy broken away in this view to reveal the protruding upper end ofthe tube 72. extending itno the chamber 86, and the upper end of theretaining screw, as seen through the valve opening formed by the groove97. The chamber 84 is visible through the valve opening formed by groove96, on the opposite side of valve web 22'.

The respective extreme positions of the valve illustrated in Figure 4are determined by the stops 104 and 195 shown in Figure 2 which areengaged by a radial protrusion 136 of the valve. Thus, as seen in thisfigure, when the valve 22 is rotated such that the protrusion 106engages the stop 1&5, as shown, the valve partition 22' is in theorientation seen in Figure 4 in which all of the gases are conductedthrough the canister. This position of the valve is designated as the onposition. When the valve is rotated to place the protrusion 196 againstthe stop 194, the partition 22 is orientated as indicated by the dottedlines in Figure 4 in which all of the gases pass directly to thedischarge outlet of the absorber and none are circulated through thecanister. This position of the valve 22 is designated as the ofiposition.

It will be apparent that the absorber apparatus now described affords anextremely compact and simple mechanism which greatly facilitates the useand maintenance thereof. When, for example, it is desired to inspect theabsorbent charge or to replace it, the canister may easily and quicklybe removed by a single operation in which the knob 56 of the retainingscrew, as shown in Figure 3, is unthreaded, whereupon the entirecanister assembly is freed of the absorber housing and may be loweredtherefrom and conveniently rested on a table or other fiat surface. Itis a further significant feature of this construction that when thecanister is emptied, the interior thereof and the down-tube assembly andscreen may be thoroughly cleaned with ease. Thus, for example, thedowntube and attached screen can be removed from the canister leavingexposed the interior of the canister, which is free of crevices orrecesses in which deposits can occur. Similarly, the removable down-tubeassembly is entirely accessible for cleaning and particularly for theremoval of deposits which tend to form on the screen during use.

A cap 108, seen in Figure 3, supported by a bead chain 109 from one ofthe radial ribs 81, is placed over the end of the tube 72 when thecanister is filled. The upper conical end 110 of the cap has a reducedsize opening through which the shaft 52 projects when the cap is placedin the down-tube, so that the absorbent is prevented from entering thetube during filling. The cap is attached to the down-tube forconvenience and may be detached and used separately if desired. It isdesirable frequently to keep on hand a filled, spare canister so thatthe absorber can be recharged without actually having to refill the samecanister. If it is desired to replace the charge during anesthesia, thevalve 22 is placed in o position, isolating the canister from theremainder of the circuit. The canister can then be replaced withoutinterrupting the patients breathing.

After refilling the canister, it may easily be returned to its originalseated position on the absorber following the procedure described aboveand the retaining screw then tightened to complete its gas tight sealingengagement. As described above, the act of placing the canister inseated position against the bottom of the absorber housing automaticallyeffects the insertion of the downtube in the opening 78 of the absorberhousing, and automatically disposes the retaining screw in aligned,confronting position to the bushing 56 for completion of the threadedengagement of these members. Thus, the entire seating operation may beaccomplished without hunting or manipulation to effect alignment. Afterthe canister has been seated, the canister bypass valve is set in itsdesired position causing a. predetermined portion of the gas flow to becirculated through the canister. When the canister by-pass valve isfully or partially open, the inletgases are permitted to pass throughthe chambers 86 and 80 of the absorber housing, downwardly through thetube 72 to the distributing chamber 76. The gases thence pass upwardlythrough the screen 74 and the charge bed supported thereon and out ofthe top of the canister through the opening 83 formed in the bottom ofthe absorber housing. These gases pass through opening 83 into chamber84 and thence to outlet chamber 88 which communicates with the absorberoutlet 18. When the canister bypass valve is only partially open, aportion of the gases delivered to the absorber will, of course, bedelivered directly to the discharge chamber 88 so as to circumvent thecanister. The path of the gases through the absorber is illustrated aspreviously mentioned in the schematic flow circuit of Figure 7. Theapparatus therein, of course, is connected to the usual administeringapparatus, such as an inhaler face mask, to complete a closed breathingcircuit in which the gases may be continuously administered and recycledto the patient. It will be understood that the various elementscomprising the flow circuit such as the check valves, the ethervaporizer, etc., may be rearranged and that an absorber may beconstructed in accordance with the present invention in which theseparts of the circuit have a different relationship'tha'n in the presentpreferred embodiment. In some instances, for example, it may be desiredto locate the various valve elements and the vaporizer apart from theabsorber housing. In other instances, it may be preferred, for example,to connect the vaporizer on the inlet side of the absorber and possiblyalso to rearrange the pressure relief valve and inhalation check valveto correspond to other frequently employed circuit arrangements.

The construction of the absorber as above described, in addition tofacilitating the operation and servicing thereof, affords a greatlyimproved distribution of the gas flow through the absorbent bed. Asbefore described, the distributing chamber 7 6 gradually diminishes incrosssectional flow area toward the outer edge of the canister. Thisproduces a manifolding effect in which the gases delivered to thechamber are distributed more uniformly in their flow upwardly throughthe screen. In addition, the inverted bottom of the canister and thecorresponding shape of the supporting screen 82 provide a vertical flowpath at the outer strata of the charge bed, immediately adjacent thewall of the canister, of greater relative length from the bottom of thecharge to the top thereof, than the corresponding vertical fiow pathformed in the inner strata immediately adjacent the tube 80.

It has been found in cylindrical charge containers that there is atendency for a greater portion of the gas to flow through the outerstrata of the charge bed adjacent to the outer walls of the container,apparently due to a re duced flow resistance in these regions. In thepresent construction, the elongation of this outer flow path tends toequalize the flow assistance throughout the bed, thus producing a moreuniform distribution of flow. This will be seen to afford a more uniformconsumption, or de pletion, of the absorbent and effect a greatereconomy in its use. A further significant advantage gained by theemployment of the device herein described results from the circulationof the gases to be treated, first downwardly through the centrallylocated tube 72, and thence upwardly through the absorbent bed which isin surrounding relation thereto. The proximity thus afforded, of thedown-tube and delivery gases to the charge bed, enables heating of theincoming gases by the heat evolved in the charge due to the chemicalreaction by which absorption of the carbon dioxide occurs. Thetemperatures, of course, are not intense, but sufi'icient heating takesplace to increase the moisture capacity of the gases, enabling the gasesto pick up a considerable portion of the moisture that is also formed asa product of the absorption reaction in the lower strata of the chargebed. Thus, the lower strata is kept relatively dry and is prevented frombecoming saturated by this moisture. Under these conditions, the chargehas less tendency to cake and form deposits on the screen 74 so that thecleaning of the screen and lower parts of the canister is greatlyfacilitated. In addition, the moisture picked up by the warmed gases iscarried upwardly through the charge bed, the top strata of whichnormally would be relatively dry. In such a dry state, the finerparticles of the charge material can be picked up by the gas and carriedinto the gas passages, requiring screens or other similar devices toprevent this occurrence. In the present arrangement, the additionalmoisture afforded in the top strata of the charge bed tends to reduce orprevent the entrainment of fine particles in the gases. Avoidance ofthis occurrence, of course, is highly desirable, not only because iteliminates the need of screen or bafiie devices, but also because iteliminates the undesired, deleterious effects produced by the causticabsorbent when deposited in other parts of the absorber.

The present invention is not limited to the specific embodiment hereindescribed, but may be used in other ways without the departure from itsspirit as defined by the following claims:

I claim:

1. A carbon dioxide absorber for anesthetic administering apparatus,comprising a housing having an annular seating surface on the bottomthereof, a detachable, cylindrical canister supported by said housing,adapted to hold a supply of carbon dioxide absorbent, having an open topreceived in substantially gas-tight engagement against said annularseating surface, first and second openings in the bottom of said housingregistering with the open top of said canister and forming a part of abreathing circuit through which gases are adapted to be circulatedthrough said canister, said first opening being concentrically disposedwith respect to said annular seating surface, a removable down-tubeassembly in said canister, including a vertical tubular memberregistering at its upper end with said first opening and having aradially extending screen at its lower end which is adapted to supportthereon a bed of the carbon dioxide absorbent, said screen being seatedon the bottom of said canister and shaped with respect thereto to form adistributing chamber at the bottom of said canister communicating withthe lower end of said tube, and means for detachably securing saidcanister to said absorber, including a threaded socket within said firstopening and a retaining screw, said retaining screw having an adjustingknob bearing against the bottom of aid canister and an elongated shaftextending upwardly 10' through said tubular member, threadedly engagedin said socket.

2. An absorber as set forth in claim 1 wherein said threaded socket isconcentrically disposed in said first opening and said retaining screwis provided with guide means axially disposing said shaft in saiddown-tube, such that when said canister is seated against said absorber,said down-tube is automatically placed in registry with said firstopening and said screw shaft is automatically aligned for threadedengagement in said socket.

3. An absorber as set forth in claim 1 wherein said retaining screw ismounted in said canister, said screw being longitudinally movable withrespect to said canister and having resilient means urging the headthereof upwardly against the bottom of said canister.

4. An absorber as set forth in claim 3 wherein the bottom of saidcanister is concave and said head portion of said screw mounted thereinis completely recessed such that the canister is self-supporting on thebottom thereof when removed from said absorber housing.

5. A carbon dioxide absorber comprising a housing adapted to beconnected to an anesthetic circuit, having a canister receiving recessat the bottom thereof and an annular seating surface therein, acylindrical canister received in said recess having an open-top seatedagainst said seating surface, a vertical down-tube carried in saidcanister having a funnel-shaped screen surrounding the lower end thereofresting on the bottom of said canister to form a distributing chambercommunicating with the lower end of said tube, a first opening in saidabsorber recess concentrically disposed relative to said annular seatingsurface and having an outwardly flared entrance, guide means forsubstantially centering said tube in said canister effective to permitthe upper end thereof to be retractably inserted in said first openingwhen said canister is seated on said absorber, a second opening in saidhousing recess registering with said canister and forming, together withsaid first opening, passage means for conducting circuit gases to andfrom said canister, a threaded socket in said absorber housingconcentrically disposed in said first opening, a retaining screw havinga head portion engaging the bottom of said canister and an elongatedshaft portion extending upwardly through said tube, adapted at its upperend to be threaded into said socket, guide means disposing saidelongated shaft member substantially centrally in said down-tube, andmeans mounting said retaining screw in said canister including resilientmeans urging said retaining screw upwardly and effective to permitrelative longitudinal displacement between said screw and said canister,said canister being adapted to be seated and secured to said a'bsorberby placing, first, one part of its upper edge in said recess and inengagement with said seating surface, and, while maintaining suchengagement, adjusting the position of said canister to bring aboutengagement of the entire upper edge of said seating surface, said tubebeing automatically inserted in said first opening and said retainingscrew being automatically aligned and resiliently 'butted against saidsocket, by said act of adjusting the position of said canister to placeit in full seated position.

6. A carbon dioxide absorber comprising a housing having an inlet and anoutlet adapted to be connected in a breathing circuit, first and secondopenings in the bottom of said housing connected respectively with saidinlet and said outlet, an annular seating surface on the bottom of saidhousing encompassing said first and second openings, a cylindricalcanister having an open top secured to said housing in engagement withsaid annular seat such that gases may be conducted to and from saidcanister through said first and second openings, said canister having aninverted concave bottom and an aperture substantially centrally disposedtherein, a threaded receptacle disposed in said housing in substantiallyconcentric, confronting relation to said canister, a retaining screwhaving an enlarged head bearing upwardly against the bottom of saidcanister and having an elongated shaft extending upwardly through saidaperture adapted to be threadedly received in said receptacle, meanscarried on said shaft for centering it in said canister, to effectalignment of said shaft with said receptacle when said canister is inseated position, spring means carried on said shaft, compress ed againstthe bottom of said canister and a portion of said shaft, such that saidretaining screw is resiliently mounted in said canister to permitrelative longitudinal displacement therebetwecn, means forming a comduit registering atits upper end with said first opening and connectingat its lower end with a distributing chamber at the bottom of saidcanister, said distributing chamber being separated from the uppercharge containing chamber of said canister by a screen adapted tosupport thereon a bed of granular absorbent material, and vaive meansinterconnecting said inlet and outlet, operable to control the How ofgas through said canister.

7. A carbon dioxide absorber for anesthetic administering apparatus inwhich a charge of carbon dioxide absorbent material is adapted to beheld and contacted with "respiratory gases conducted therethroughcomprising a cylindrical, open-top shell forming a canister for holdingsaid absorbent charge, a removable down-tube unit disposed in saidcanister, including a vertically extending tube having radial projectingmeans arranged to slidably contact the side wall of said canister forpositioning said tube therein, and a screen, encircling said tube at thelower end portion thereof and extending outwardly therefrom, said screenat its outer peripheral end portion bearing against a wall portion ofsaid canister and forming in the lower region of said canister adistributing chamber communicating with the lower end of said tube, thespace above said screen communicating with said distributing chamberthrough the perforations of said screen and forming a chamber in which acharge of absorbent material is adapted to be held and supported on saidscreen, a housing having gas passages through which respiratory gasesare adapted to be circulated, means on the underside of said housing forreceiving the upper, open end of said canister thereagainst, includingat least two separate ports through which the respiratory gases in saidgas passages are adapted to be delivered to and from said canisterrespectively, said canister receiving means being effective to registersaid ports with the top of said canister and to register one of saidopenings with the upper end of said vertical tube, and externallyaccessible retaining means operable to detachably secure said canisteragainst said canister receiving means.

8. A carbon dioxide absorber according to claim 7 end with said housingto hold said canister in gas-tight engagement therewith.

9. A carbon dioxide absorber according to claim 8 wherein said retainingmeans has an externally accessible manually adjustable portionengageable with the underside of said canister and said canister isrecessed at the bottom thereof to accommodate said retaining meansportion therein and efiectively present a self-supporting basepermitting said canister to be placed in an upright position on a fiatsurface when said canister is detached from said housing.

1.0. An absorber for anesthetic administering apparatus comprising ahousing having an inelt and an outlet adapted to be connected in abreathing circuit and communicating respectively with first and secondopenings in the bottom of said housing, a detachable canister forholding a supply of a carbon dioxide absorbent having an open topreceived against said housing so as to encompass said first and secondbottom openings, a removable down- 12 tube assembly carried in saidcanister including a substantially axially disposed vertical tubularmember and a screen member forming an annular skirt extending outwardlyand downwardly from the lower portion of said tubular member, saidtubular member registering at its upper end with one of said openingsand said screen having a cone shape and extending outwardly to the sidewalls of said canister to form in the space below said screen adistributing chamber communicating with the lower end of said tubularmember and effectively separating said chamber from the space thereabovein said canister in which is adapted to be placed a charge of absorbentmaterial, said canister having an inverted, conical bottom face whoseaxis is substantially concentric with and whose apex angle is relativelygreater than that of said conically shaped screen member, such that saiddistributing chamber has a progressively diminishing crosssectional flowarea at successively greater radial incremerits, and externallyaccessible retaining means engageable with the underside of saidcanister extending upwardly therethrough and detachably engaging withsaid housing to effectively secure said canister in gastight engagementtherewith.

11. An absorber as set forth in claim 10 wherein said retaining meanscomprises a screw having an elongated shaft co-axially disposed in saidtubular member, threadedly engaging said housing at its upper end andhaving a knob with a spherical bearing surface engaging the conicalbottom of said canister.

12. A carbon dioxide absorber for anesthetic administering apparatuscomprising a housing adapted to be connected in an anesthetic breathingcircuit and having passages therein for conducting said respiratorygases therethrough, including at least two separate gas ports in abottom face thereof, a cylindrical open-top shell forming a canister forholding a charge of carbon dioxide absorbent material dctachably securedto the underside of said housing such that the open top thereofregisters with said gas ports formed in the bottom of said housing, aremovable down-tube unit carried in said canister including a verticallyextending tube positioned longitudinally, substantially centrallyrelative to the side walls of said canister, registering at its upperend with one of said gas ports, and a rigid screen member surroundingand extending outwardly at the lower end portion thereof from said tubeto the cylindrical side walls of said canister, said screen member beingof a cone-like configuration extending outwardly and downwardly fromsaid central tube and resting at its outer edge against the bottom ofsaid canister to thereby support said downtube unit, said screen formingin the bottom of said canister an outwardly extending distributingchamber communicating with the lower end of central tube and formingabove said screen a charge chamber, wherein a body of said carbondioxide absorbent charge is adapted to be supported on said screen, towhich gases maypass from said distributing chamber through said screen,said charge chamber having a progressively greater vertical extent in anoutward radial direction such that respiratory gases passed downwardlythrough said tube to said distributing chamber and upwardly through abody of charge mrv terial in said charge chamber are substantiallyuniformly distributed throughout the cross-sectional flow area thereofand wherein the flow path adjacent the outer cylindrical wall of saidcanister constitutes the maxi mum length of flow path'in said chargebed.

References Cited in the file of this patent UNITED STATES PATENTS2,121,196 Heidbrink June 21, 1938 2,614,561 Fox Oct. 21, 1952

1. A CORBON DIOXIDE ABSORBER FOR ANESTHETIC ADMINISTERING APPARATUS,COMPRISING A HOUSING HAVING AN ANNULAR SEATING SURFACE ON THE BOTTOMTHEREOF, A DETACHABLE, CYLINDRICAL CANISTER SUPPORTED BY SAID HOUSING,ADAPTED TO HOLD A SUPPLY OF CARBON DIOXIDE ABSORBENT, HAVING AN OPEN TOPRECEIVED IN SUB STANTIALLY GAS-TIGHT ENGAGEMENT AGAINST SAID ANNULARSEATING SURFACE, FIRST AND SECOND OPENINGS IN THE BOTTOM OF SAID HOUSINGREGISTERING WITH THE OPEN TOP OF SAID CANISTER AND FORMING A PART OF ABREATHING CIRCUIT THROUGH WHICH GASES ARE ADAPTED TO BE CIRCULATEDTHROUGH SAID CANISTER, SAID FIRST OPENING BEING CONCENTRICALLY DISPOSEDWITH RESPECT TO SAID ANNULAR SEATING SURFACE, A REMOVABLE DOWN-TUBEASSEMBLY IN SAID CANISTER, INCLUDING A VERTICAL TUBULAR MEMBERREGISTERING AT ITS UPPER END WITH SAID FIRST OPENING AND HAVING ARADIALLY EXTENDING SCREEN AT ITS LOWER END WHICH IS ADAPTED TO SUPPORTTHEREON A BED OF THE CARBON DIOXIDE ABSORBENT, SAID SCREEN BEING SEATEDON THE BOTTOM OF SAID CANISTER AND SHAPED WITH RESPECT THERETO TO FORM ADISTRIBUTING CHAMBER AT THE BOTTOM OF SAID CANISTER COMMUNICATING WITHTHE LOWER END OF SAID TUBE, AND MEANS FEOR DETACHABLY SECURING SAIDCANISTER TO SAID ABSORBER, INCLUDING A THREADED SOCKET WITHIN SAID FIRSTOPENING AND A RETAINING SCREW, SAID RETAINING SCREW HAVING AN ADJUSTINGKNOB BEARING AGAINST THE BOTTOM OF SAID CANISTER AND AN ELONGATED SHAFTEXTENDING UPWARDLY THROUGH SAID TUBULAR MEMBER, THREADEDLY ENGAGED INSAID SOCKET.